Merge lp:~tribaal/charms/trusty/mysql/charm-helpers-sync into lp:charms/trusty/mysql

[Chris Glass]

This branch updates charm-helpers so that the charm take advantage of the new in-memory apt-cache building (fixes race conditions).

[Review Queue (review-queue)]

This items has failed automated testing! Results available here http://reports.vapour.ws/charm-tests/charm-bundle-test-1109-results

review: Needs Fixing (automated testing)

[David Britton (dpb)]

Look great Chris, Thanks! -- I checked the automated test results, the error was from hpcloud and was spurious.

review: Approve

=== added file '.bzrignore'
--- .bzrignore	1970-01-01 00:00:00 +0000
+++ .bzrignore	2014-09-26 07:21:45 +0000
@@ -0,0 +1,1 @@
+bin/
 
=== modified file 'Makefile'
--- Makefile	2014-03-04 17:28:10 +0000
+++ Makefile	2014-09-26 07:21:45 +0000
@@ -11,5 +11,10 @@
 #	@echo Starting tests...
 #	@$(PYTHON) /usr/bin/nosetests --nologcapture unit_tests
 
-sync:
-	@charm-helper-sync -c charm-helpers.yaml
+bin/charm_helpers_sync.py:
+	@mkdir -p bin
+	@bzr cat lp:charm-helpers/tools/charm_helpers_sync/charm_helpers_sync.py \
+        > bin/charm_helpers_sync.py
+
+sync: bin/charm_helpers_sync.py
+	$(PYTHON) bin/charm_helpers_sync.py -c charm-helpers.yaml
 
=== added file 'hooks/charmhelpers/core/fstab.py'
--- hooks/charmhelpers/core/fstab.py	1970-01-01 00:00:00 +0000
+++ hooks/charmhelpers/core/fstab.py	2014-09-26 07:21:45 +0000
@@ -0,0 +1,116 @@
+#!/usr/bin/env python
+# -*- coding: utf-8 -*-
+
+__author__ = 'Jorge Niedbalski R. <[e-mail]>'
+
+import os
+
+
+class Fstab(file):
+    """This class extends file in order to implement a file reader/writer
+    for file `/etc/fstab`
+    """
+
+    class Entry(object):
+        """Entry class represents a non-comment line on the `/etc/fstab` file
+        """
+        def __init__(self, device, mountpoint, filesystem,
+                     options, d=0, p=0):
+            self.device = device
+            self.mountpoint = mountpoint
+            self.filesystem = filesystem
+
+            if not options:
+                options = "defaults"
+
+            self.options = options
+            self.d = d
+            self.p = p
+
+        def __eq__(self, o):
+            return str(self) == str(o)
+
+        def __str__(self):
+            return "{} {} {} {} {} {}".format(self.device,
+                                              self.mountpoint,
+                                              self.filesystem,
+                                              self.options,
+                                              self.d,
+                                              self.p)
+
+    DEFAULT_PATH = os.path.join(os.path.sep, 'etc', 'fstab')
+
+    def __init__(self, path=None):
+        if path:
+            self._path = path
+        else:
+            self._path = self.DEFAULT_PATH
+        file.__init__(self, self._path, 'r+')
+
+    def _hydrate_entry(self, line):
+        # NOTE: use split with no arguments to split on any
+        #       whitespace including tabs
+        return Fstab.Entry(*filter(
+            lambda x: x not in ('', None),
+            line.strip("\n").split()))
+
+    @property
+    def entries(self):
+        self.seek(0)
+        for line in self.readlines():
+            try:
+                if not line.startswith("#"):
+                    yield self._hydrate_entry(line)
+            except ValueError:
+                pass
+
+    def get_entry_by_attr(self, attr, value):
+        for entry in self.entries:
+            e_attr = getattr(entry, attr)
+            if e_attr == value:
+                return entry
+        return None
+
+    def add_entry(self, entry):
+        if self.get_entry_by_attr('device', entry.device):
+            return False
+
+        self.write(str(entry) + '\n')
+        self.truncate()
+        return entry
+
+    def remove_entry(self, entry):
+        self.seek(0)
+
+        lines = self.readlines()
+
+        found = False
+        for index, line in enumerate(lines):
+            if not line.startswith("#"):
+                if self._hydrate_entry(line) == entry:
+                    found = True
+                    break
+
+        if not found:
+            return False
+
+        lines.remove(line)
+
+        self.seek(0)
+        self.write(''.join(lines))
+        self.truncate()
+        return True
+
+    @classmethod
+    def remove_by_mountpoint(cls, mountpoint, path=None):
+        fstab = cls(path=path)
+        entry = fstab.get_entry_by_attr('mountpoint', mountpoint)
+        if entry:
+            return fstab.remove_entry(entry)
+        return False
+
+    @classmethod
+    def add(cls, device, mountpoint, filesystem, options=None, path=None):
+        return cls(path=path).add_entry(Fstab.Entry(device,
+                                                    mountpoint, filesystem,
+                                                    options=options))
 
=== modified file 'hooks/charmhelpers/core/hookenv.py'
--- hooks/charmhelpers/core/hookenv.py	2014-02-19 14:49:31 +0000
+++ hooks/charmhelpers/core/hookenv.py	2014-09-26 07:21:45 +0000
@@ -25,7 +25,7 @@
 def cached(func):
     """Cache return values for multiple executions of func + args
 
-    For example:
+    For example::
 
         @cached
         def unit_get(attribute):
@@ -155,6 +155,121 @@
     return os.path.basename(sys.argv[0])
 
 
+class Config(dict):
+    """A dictionary representation of the charm's config.yaml, with some
+    extra features:
+
+    - See which values in the dictionary have changed since the previous hook.
+    - For values that have changed, see what the previous value was.
+    - Store arbitrary data for use in a later hook.
+
+    NOTE: Do not instantiate this object directly - instead call
+    ``hookenv.config()``, which will return an instance of :class:`Config`.
+
+    Example usage::
+
+        >>> # inside a hook
+        >>> from charmhelpers.core import hookenv
+        >>> config = hookenv.config()
+        >>> config['foo']
+        'bar'
+        >>> # store a new key/value for later use
+        >>> config['mykey'] = 'myval'
+
+
+        >>> # user runs `juju set mycharm foo=baz`
+        >>> # now we're inside subsequent config-changed hook
+        >>> config = hookenv.config()
+        >>> config['foo']
+        'baz'
+        >>> # test to see if this val has changed since last hook
+        >>> config.changed('foo')
+        True
+        >>> # what was the previous value?
+        >>> config.previous('foo')
+        'bar'
+        >>> # keys/values that we add are preserved across hooks
+        >>> config['mykey']
+        'myval'
+
+    """
+    CONFIG_FILE_NAME = '.juju-persistent-config'
+
+    def __init__(self, *args, **kw):
+        super(Config, self).__init__(*args, **kw)
+        self.implicit_save = True
+        self._prev_dict = None
+        self.path = os.path.join(charm_dir(), Config.CONFIG_FILE_NAME)
+        if os.path.exists(self.path):
+            self.load_previous()
+
+    def __getitem__(self, key):
+        """For regular dict lookups, check the current juju config first,
+        then the previous (saved) copy. This ensures that user-saved values
+        will be returned by a dict lookup.
+
+        """
+        try:
+            return dict.__getitem__(self, key)
+        except KeyError:
+            return (self._prev_dict or {})[key]
+
+    def load_previous(self, path=None):
+        """Load previous copy of config from disk.
+
+        In normal usage you don't need to call this method directly - it
+        is called automatically at object initialization.
+
+        :param path:
+
+            File path from which to load the previous config. If `None`,
+            config is loaded from the default location. If `path` is
+            specified, subsequent `save()` calls will write to the same
+            path.
+
+        """
+        self.path = path or self.path
+        with open(self.path) as f:
+            self._prev_dict = json.load(f)
+
+    def changed(self, key):
+        """Return True if the current value for this key is different from
+        the previous value.
+
+        """
+        if self._prev_dict is None:
+            return True
+        return self.previous(key) != self.get(key)
+
+    def previous(self, key):
+        """Return previous value for this key, or None if there
+        is no previous value.
+
+        """
+        if self._prev_dict:
+            return self._prev_dict.get(key)
+        return None
+
+    def save(self):
+        """Save this config to disk.
+
+        If the charm is using the :mod:`Services Framework <services.base>`
+        or :meth:'@hook <Hooks.hook>' decorator, this
+        is called automatically at the end of successful hook execution.
+        Otherwise, it should be called directly by user code.
+
+        To disable automatic saves, set ``implicit_save=False`` on this
+        instance.
+
+        """
+        if self._prev_dict:
+            for k, v in self._prev_dict.iteritems():
+                if k not in self:
+                    self[k] = v
+        with open(self.path, 'w') as f:
+            json.dump(self, f)
+
+
 @cached
 def config(scope=None):
     """Juju charm configuration"""
@@ -163,7 +278,10 @@
         config_cmd_line.append(scope)
     config_cmd_line.append('--format=json')
     try:
-        return json.loads(subprocess.check_output(config_cmd_line))
+        config_data = json.loads(subprocess.check_output(config_cmd_line))
+        if scope is not None:
+            return config_data
+        return Config(config_data)
     except ValueError:
         return None
 
@@ -188,8 +306,9 @@
         raise
 
 
-def relation_set(relation_id=None, relation_settings={}, **kwargs):
+def relation_set(relation_id=None, relation_settings=None, **kwargs):
     """Set relation information for the current unit"""
+    relation_settings = relation_settings if relation_settings else {}
     relation_cmd_line = ['relation-set']
     if relation_id is not None:
         relation_cmd_line.extend(('-r', relation_id))
@@ -348,27 +467,29 @@
 class Hooks(object):
     """A convenient handler for hook functions.
 
-    Example:
+    Example::
+
         hooks = Hooks()
 
         # register a hook, taking its name from the function name
         @hooks.hook()
         def install():
-            ...
+            pass  # your code here
 
         # register a hook, providing a custom hook name
         @hooks.hook("config-changed")
         def config_changed():
-            ...
+            pass  # your code here
 
         if __name__ == "__main__":
             # execute a hook based on the name the program is called by
             hooks.execute(sys.argv)
     """
 
-    def __init__(self):
+    def __init__(self, config_save=True):
         super(Hooks, self).__init__()
         self._hooks = {}
+        self._config_save = config_save
 
     def register(self, name, function):
         """Register a hook"""
@@ -379,6 +500,10 @@
         hook_name = os.path.basename(args[0])
         if hook_name in self._hooks:
             self._hooks[hook_name]()
+            if self._config_save:
+                cfg = config()
+                if cfg.implicit_save:
+                    cfg.save()
         else:
             raise UnregisteredHookError(hook_name)
 
 
=== modified file 'hooks/charmhelpers/core/host.py'
--- hooks/charmhelpers/core/host.py	2014-02-19 14:49:31 +0000
+++ hooks/charmhelpers/core/host.py	2014-09-26 07:21:45 +0000
@@ -12,10 +12,13 @@
 import string
 import subprocess
 import hashlib
+import shutil
+from contextlib import contextmanager
 
 from collections import OrderedDict
 
 from hookenv import log
+from fstab import Fstab
 
 
 def service_start(service_name):
@@ -34,7 +37,8 @@
 
 
 def service_reload(service_name, restart_on_failure=False):
-    """Reload a system service, optionally falling back to restart if reload fails"""
+    """Reload a system service, optionally falling back to restart if
+    reload fails"""
     service_result = service('reload', service_name)
     if not service_result and restart_on_failure:
         service_result = service('restart', service_name)
@@ -50,7 +54,7 @@
 def service_running(service):
     """Determine whether a system service is running"""
     try:
-        output = subprocess.check_output(['service', service, 'status'])
+        output = subprocess.check_output(['service', service, 'status'], stderr=subprocess.STDOUT)
     except subprocess.CalledProcessError:
         return False
     else:
@@ -60,6 +64,16 @@
             return False
 
 
+def service_available(service_name):
+    """Determine whether a system service is available"""
+    try:
+        subprocess.check_output(['service', service_name, 'status'], stderr=subprocess.STDOUT)
+    except subprocess.CalledProcessError as e:
+        return 'unrecognized service' not in e.output
+    else:
+        return True
+
+
 def adduser(username, password=None, shell='/bin/bash', system_user=False):
     """Add a user to the system"""
     try:
@@ -143,7 +157,19 @@
         target.write(content)
 
 
-def mount(device, mountpoint, options=None, persist=False):
+def fstab_remove(mp):
+    """Remove the given mountpoint entry from /etc/fstab
+    """
+    return Fstab.remove_by_mountpoint(mp)
+
+
+def fstab_add(dev, mp, fs, options=None):
+    """Adds the given device entry to the /etc/fstab file
+    """
+    return Fstab.add(dev, mp, fs, options=options)
+
+
+def mount(device, mountpoint, options=None, persist=False, filesystem="ext3"):
     """Mount a filesystem at a particular mountpoint"""
     cmd_args = ['mount']
     if options is not None:
@@ -154,9 +180,9 @@
     except subprocess.CalledProcessError, e:
         log('Error mounting {} at {}\n{}'.format(device, mountpoint, e.output))
         return False
+
     if persist:
-        # TODO: update fstab
-        pass
+        return fstab_add(device, mountpoint, filesystem, options=options)
     return True
 
 
@@ -168,9 +194,9 @@
     except subprocess.CalledProcessError, e:
         log('Error unmounting {}\n{}'.format(mountpoint, e.output))
         return False
+
     if persist:
-        # TODO: update fstab
-        pass
+        return fstab_remove(mountpoint)
     return True
 
 
@@ -183,10 +209,15 @@
     return system_mounts
 
 
-def file_hash(path):
-    """Generate a md5 hash of the contents of 'path' or None if not found """
+def file_hash(path, hash_type='md5'):
+    """
+    Generate a hash checksum of the contents of 'path' or None if not found.
+
+    :param str hash_type: Any hash alrgorithm supported by :mod:`hashlib`,
+                          such as md5, sha1, sha256, sha512, etc.
+    """
     if os.path.exists(path):
-        h = hashlib.md5()
+        h = getattr(hashlib, hash_type)()
         with open(path, 'r') as source:
             h.update(source.read())  # IGNORE:E1101 - it does have update
         return h.hexdigest()
@@ -194,16 +225,36 @@
         return None
 
 
+def check_hash(path, checksum, hash_type='md5'):
+    """
+    Validate a file using a cryptographic checksum.
+
+    :param str checksum: Value of the checksum used to validate the file.
+    :param str hash_type: Hash algorithm used to generate `checksum`.
+        Can be any hash alrgorithm supported by :mod:`hashlib`,
+        such as md5, sha1, sha256, sha512, etc.
+    :raises ChecksumError: If the file fails the checksum
+
+    """
+    actual_checksum = file_hash(path, hash_type)
+    if checksum != actual_checksum:
+        raise ChecksumError("'%s' != '%s'" % (checksum, actual_checksum))
+
+
+class ChecksumError(ValueError):
+    pass
+
+
 def restart_on_change(restart_map, stopstart=False):
     """Restart services based on configuration files changing
 
-    This function is used a decorator, for example
+    This function is used a decorator, for example::
 
         @restart_on_change({
             '/etc/ceph/ceph.conf': [ 'cinder-api', 'cinder-volume' ]
             })
         def ceph_client_changed():
-            ...
+            pass  # your code here
 
     In this example, the cinder-api and cinder-volume services
     would be restarted if /etc/ceph/ceph.conf is changed by the
@@ -295,3 +346,40 @@
     if 'link/ether' in words:
         hwaddr = words[words.index('link/ether') + 1]
     return hwaddr
+
+
+def cmp_pkgrevno(package, revno, pkgcache=None):
+    '''Compare supplied revno with the revno of the installed package
+
+    *  1 => Installed revno is greater than supplied arg
+    *  0 => Installed revno is the same as supplied arg
+    * -1 => Installed revno is less than supplied arg
+
+    '''
+    import apt_pkg
+    from charmhelpers.fetch import apt_cache
+    if not pkgcache:
+        pkgcache = apt_cache()
+    pkg = pkgcache[package]
+    return apt_pkg.version_compare(pkg.current_ver.ver_str, revno)
+
+
+@contextmanager
+def chdir(d):
+    cur = os.getcwd()
+    try:
+        yield os.chdir(d)
+    finally:
+        os.chdir(cur)
+
+
+def chownr(path, owner, group):
+    uid = pwd.getpwnam(owner).pw_uid
+    gid = grp.getgrnam(group).gr_gid
+
+    for root, dirs, files in os.walk(path):
+        for name in dirs + files:
+            full = os.path.join(root, name)
+            broken_symlink = os.path.lexists(full) and not os.path.exists(full)
+            if not broken_symlink:
+                os.chown(full, uid, gid)
 
=== added directory 'hooks/charmhelpers/core/services'
=== added file 'hooks/charmhelpers/core/services/__init__.py'
--- hooks/charmhelpers/core/services/__init__.py	1970-01-01 00:00:00 +0000
+++ hooks/charmhelpers/core/services/__init__.py	2014-09-26 07:21:45 +0000
@@ -0,0 +1,2 @@
+from .base import *
+from .helpers import *
 
=== added file 'hooks/charmhelpers/core/services/base.py'
--- hooks/charmhelpers/core/services/base.py	1970-01-01 00:00:00 +0000
+++ hooks/charmhelpers/core/services/base.py	2014-09-26 07:21:45 +0000
@@ -0,0 +1,313 @@
+import os
+import re
+import json
+from collections import Iterable
+
+from charmhelpers.core import host
+from charmhelpers.core import hookenv
+
+
+__all__ = ['ServiceManager', 'ManagerCallback',
+           'PortManagerCallback', 'open_ports', 'close_ports', 'manage_ports',
+           'service_restart', 'service_stop']
+
+
+class ServiceManager(object):
+    def __init__(self, services=None):
+        """
+        Register a list of services, given their definitions.
+
+        Service definitions are dicts in the following formats (all keys except
+        'service' are optional)::
+
+            {
+                "service": <service name>,
+                "required_data": <list of required data contexts>,
+                "provided_data": <list of provided data contexts>,
+                "data_ready": <one or more callbacks>,
+                "data_lost": <one or more callbacks>,
+                "start": <one or more callbacks>,
+                "stop": <one or more callbacks>,
+                "ports": <list of ports to manage>,
+            }
+
+        The 'required_data' list should contain dicts of required data (or
+        dependency managers that act like dicts and know how to collect the data).
+        Only when all items in the 'required_data' list are populated are the list
+        of 'data_ready' and 'start' callbacks executed.  See `is_ready()` for more
+        information.
+
+        The 'provided_data' list should contain relation data providers, most likely
+        a subclass of :class:`charmhelpers.core.services.helpers.RelationContext`,
+        that will indicate a set of data to set on a given relation.
+
+        The 'data_ready' value should be either a single callback, or a list of
+        callbacks, to be called when all items in 'required_data' pass `is_ready()`.
+        Each callback will be called with the service name as the only parameter.
+        After all of the 'data_ready' callbacks are called, the 'start' callbacks
+        are fired.
+
+        The 'data_lost' value should be either a single callback, or a list of
+        callbacks, to be called when a 'required_data' item no longer passes
+        `is_ready()`.  Each callback will be called with the service name as the
+        only parameter.  After all of the 'data_lost' callbacks are called,
+        the 'stop' callbacks are fired.
+
+        The 'start' value should be either a single callback, or a list of
+        callbacks, to be called when starting the service, after the 'data_ready'
+        callbacks are complete.  Each callback will be called with the service
+        name as the only parameter.  This defaults to
+        `[host.service_start, services.open_ports]`.
+
+        The 'stop' value should be either a single callback, or a list of
+        callbacks, to be called when stopping the service.  If the service is
+        being stopped because it no longer has all of its 'required_data', this
+        will be called after all of the 'data_lost' callbacks are complete.
+        Each callback will be called with the service name as the only parameter.
+        This defaults to `[services.close_ports, host.service_stop]`.
+
+        The 'ports' value should be a list of ports to manage.  The default
+        'start' handler will open the ports after the service is started,
+        and the default 'stop' handler will close the ports prior to stopping
+        the service.
+
+
+        Examples:
+
+        The following registers an Upstart service called bingod that depends on
+        a mongodb relation and which runs a custom `db_migrate` function prior to
+        restarting the service, and a Runit service called spadesd::
+
+            manager = services.ServiceManager([
+                {
+                    'service': 'bingod',
+                    'ports': [80, 443],
+                    'required_data': [MongoRelation(), config(), {'my': 'data'}],
+                    'data_ready': [
+                        services.template(source='bingod.conf'),
+                        services.template(source='bingod.ini',
+                                          target='/etc/bingod.ini',
+                                          owner='bingo', perms=0400),
+                    ],
+                },
+                {
+                    'service': 'spadesd',
+                    'data_ready': services.template(source='spadesd_run.j2',
+                                                    target='/etc/sv/spadesd/run',
+                                                    perms=0555),
+                    'start': runit_start,
+                    'stop': runit_stop,
+                },
+            ])
+            manager.manage()
+        """
+        self._ready_file = os.path.join(hookenv.charm_dir(), 'READY-SERVICES.json')
+        self._ready = None
+        self.services = {}
+        for service in services or []:
+            service_name = service['service']
+            self.services[service_name] = service
+
+    def manage(self):
+        """
+        Handle the current hook by doing The Right Thing with the registered services.
+        """
+        hook_name = hookenv.hook_name()
+        if hook_name == 'stop':
+            self.stop_services()
+        else:
+            self.provide_data()
+            self.reconfigure_services()
+        cfg = hookenv.config()
+        if cfg.implicit_save:
+            cfg.save()
+
+    def provide_data(self):
+        """
+        Set the relation data for each provider in the ``provided_data`` list.
+
+        A provider must have a `name` attribute, which indicates which relation
+        to set data on, and a `provide_data()` method, which returns a dict of
+        data to set.
+        """
+        hook_name = hookenv.hook_name()
+        for service in self.services.values():
+            for provider in service.get('provided_data', []):
+                if re.match(r'{}-relation-(joined|changed)'.format(provider.name), hook_name):
+                    data = provider.provide_data()
+                    _ready = provider._is_ready(data) if hasattr(provider, '_is_ready') else data
+                    if _ready:
+                        hookenv.relation_set(None, data)
+
+    def reconfigure_services(self, *service_names):
+        """
+        Update all files for one or more registered services, and,
+        if ready, optionally restart them.
+
+        If no service names are given, reconfigures all registered services.
+        """
+        for service_name in service_names or self.services.keys():
+            if self.is_ready(service_name):
+                self.fire_event('data_ready', service_name)
+                self.fire_event('start', service_name, default=[
+                    service_restart,
+                    manage_ports])
+                self.save_ready(service_name)
+            else:
+                if self.was_ready(service_name):
+                    self.fire_event('data_lost', service_name)
+                self.fire_event('stop', service_name, default=[
+                    manage_ports,
+                    service_stop])
+                self.save_lost(service_name)
+
+    def stop_services(self, *service_names):
+        """
+        Stop one or more registered services, by name.
+
+        If no service names are given, stops all registered services.
+        """
+        for service_name in service_names or self.services.keys():
+            self.fire_event('stop', service_name, default=[
+                manage_ports,
+                service_stop])
+
+    def get_service(self, service_name):
+        """
+        Given the name of a registered service, return its service definition.
+        """
+        service = self.services.get(service_name)
+        if not service:
+            raise KeyError('Service not registered: %s' % service_name)
+        return service
+
+    def fire_event(self, event_name, service_name, default=None):
+        """
+        Fire a data_ready, data_lost, start, or stop event on a given service.
+        """
+        service = self.get_service(service_name)
+        callbacks = service.get(event_name, default)
+        if not callbacks:
+            return
+        if not isinstance(callbacks, Iterable):
+            callbacks = [callbacks]
+        for callback in callbacks:
+            if isinstance(callback, ManagerCallback):
+                callback(self, service_name, event_name)
+            else:
+                callback(service_name)
+
+    def is_ready(self, service_name):
+        """
+        Determine if a registered service is ready, by checking its 'required_data'.
+
+        A 'required_data' item can be any mapping type, and is considered ready
+        if `bool(item)` evaluates as True.
+        """
+        service = self.get_service(service_name)
+        reqs = service.get('required_data', [])
+        return all(bool(req) for req in reqs)
+
+    def _load_ready_file(self):
+        if self._ready is not None:
+            return
+        if os.path.exists(self._ready_file):
+            with open(self._ready_file) as fp:
+                self._ready = set(json.load(fp))
+        else:
+            self._ready = set()
+
+    def _save_ready_file(self):
+        if self._ready is None:
+            return
+        with open(self._ready_file, 'w') as fp:
+            json.dump(list(self._ready), fp)
+
+    def save_ready(self, service_name):
+        """
+        Save an indicator that the given service is now data_ready.
+        """
+        self._load_ready_file()
+        self._ready.add(service_name)
+        self._save_ready_file()
+
+    def save_lost(self, service_name):
+        """
+        Save an indicator that the given service is no longer data_ready.
+        """
+        self._load_ready_file()
+        self._ready.discard(service_name)
+        self._save_ready_file()
+
+    def was_ready(self, service_name):
+        """
+        Determine if the given service was previously data_ready.
+        """
+        self._load_ready_file()
+        return service_name in self._ready
+
+
+class ManagerCallback(object):
+    """
+    Special case of a callback that takes the `ServiceManager` instance
+    in addition to the service name.
+
+    Subclasses should implement `__call__` which should accept three parameters:
+
+        * `manager`       The `ServiceManager` instance
+        * `service_name`  The name of the service it's being triggered for
+        * `event_name`    The name of the event that this callback is handling
+    """
+    def __call__(self, manager, service_name, event_name):
+        raise NotImplementedError()
+
+
+class PortManagerCallback(ManagerCallback):
+    """
+    Callback class that will open or close ports, for use as either
+    a start or stop action.
+    """
+    def __call__(self, manager, service_name, event_name):
+        service = manager.get_service(service_name)
+        new_ports = service.get('ports', [])
+        port_file = os.path.join(hookenv.charm_dir(), '.{}.ports'.format(service_name))
+        if os.path.exists(port_file):
+            with open(port_file) as fp:
+                old_ports = fp.read().split(',')
+            for old_port in old_ports:
+                if bool(old_port):
+                    old_port = int(old_port)
+                    if old_port not in new_ports:
+                        hookenv.close_port(old_port)
+        with open(port_file, 'w') as fp:
+            fp.write(','.join(str(port) for port in new_ports))
+        for port in new_ports:
+            if event_name == 'start':
+                hookenv.open_port(port)
+            elif event_name == 'stop':
+                hookenv.close_port(port)
+
+
+def service_stop(service_name):
+    """
+    Wrapper around host.service_stop to prevent spurious "unknown service"
+    messages in the logs.
+    """
+    if host.service_running(service_name):
+        host.service_stop(service_name)
+
+
+def service_restart(service_name):
+    """
+    Wrapper around host.service_restart to prevent spurious "unknown service"
+    messages in the logs.
+    """
+    if host.service_available(service_name):
+        if host.service_running(service_name):
+            host.service_restart(service_name)
+        else:
+            host.service_start(service_name)
+
+
+# Convenience aliases
+open_ports = close_ports = manage_ports = PortManagerCallback()
 
=== added file 'hooks/charmhelpers/core/services/helpers.py'
--- hooks/charmhelpers/core/services/helpers.py	1970-01-01 00:00:00 +0000
+++ hooks/charmhelpers/core/services/helpers.py	2014-09-26 07:21:45 +0000
@@ -0,0 +1,239 @@
+import os
+import yaml
+from charmhelpers.core import hookenv
+from charmhelpers.core import templating
+
+from charmhelpers.core.services.base import ManagerCallback
+
+
+__all__ = ['RelationContext', 'TemplateCallback',
+           'render_template', 'template']
+
+
+class RelationContext(dict):
+    """
+    Base class for a context generator that gets relation data from juju.
+
+    Subclasses must provide the attributes `name`, which is the name of the
+    interface of interest, `interface`, which is the type of the interface of
+    interest, and `required_keys`, which is the set of keys required for the
+    relation to be considered complete.  The data for all interfaces matching
+    the `name` attribute that are complete will used to populate the dictionary
+    values (see `get_data`, below).
+
+    The generated context will be namespaced under the relation :attr:`name`,
+    to prevent potential naming conflicts.
+
+    :param str name: Override the relation :attr:`name`, since it can vary from charm to charm
+    :param list additional_required_keys: Extend the list of :attr:`required_keys`
+    """
+    name = None
+    interface = None
+    required_keys = []
+
+    def __init__(self, name=None, additional_required_keys=None):
+        if name is not None:
+            self.name = name
+        if additional_required_keys is not None:
+            self.required_keys.extend(additional_required_keys)
+        self.get_data()
+
+    def __bool__(self):
+        """
+        Returns True if all of the required_keys are available.
+        """
+        return self.is_ready()
+
+    __nonzero__ = __bool__
+
+    def __repr__(self):
+        return super(RelationContext, self).__repr__()
+
+    def is_ready(self):
+        """
+        Returns True if all of the `required_keys` are available from any units.
+        """
+        ready = len(self.get(self.name, [])) > 0
+        if not ready:
+            hookenv.log('Incomplete relation: {}'.format(self.__class__.__name__), hookenv.DEBUG)
+        return ready
+
+    def _is_ready(self, unit_data):
+        """
+        Helper method that tests a set of relation data and returns True if
+        all of the `required_keys` are present.
+        """
+        return set(unit_data.keys()).issuperset(set(self.required_keys))
+
+    def get_data(self):
+        """
+        Retrieve the relation data for each unit involved in a relation and,
+        if complete, store it in a list under `self[self.name]`.  This
+        is automatically called when the RelationContext is instantiated.
+
+        The units are sorted lexographically first by the service ID, then by
+        the unit ID.  Thus, if an interface has two other services, 'db:1'
+        and 'db:2', with 'db:1' having two units, 'wordpress/0' and 'wordpress/1',
+        and 'db:2' having one unit, 'mediawiki/0', all of which have a complete
+        set of data, the relation data for the units will be stored in the
+        order: 'wordpress/0', 'wordpress/1', 'mediawiki/0'.
+
+        If you only care about a single unit on the relation, you can just
+        access it as `{{ interface[0]['key'] }}`.  However, if you can at all
+        support multiple units on a relation, you should iterate over the list,
+        like::
+
+            {% for unit in interface -%}
+                {{ unit['key'] }}{% if not loop.last %},{% endif %}
+            {%- endfor %}
+
+        Note that since all sets of relation data from all related services and
+        units are in a single list, if you need to know which service or unit a
+        set of data came from, you'll need to extend this class to preserve
+        that information.
+        """
+        if not hookenv.relation_ids(self.name):
+            return
+
+        ns = self.setdefault(self.name, [])
+        for rid in sorted(hookenv.relation_ids(self.name)):
+            for unit in sorted(hookenv.related_units(rid)):
+                reldata = hookenv.relation_get(rid=rid, unit=unit)
+                if self._is_ready(reldata):
+                    ns.append(reldata)
+
+    def provide_data(self):
+        """
+        Return data to be relation_set for this interface.
+        """
+        return {}
+
+
+class MysqlRelation(RelationContext):
+    """
+    Relation context for the `mysql` interface.
+
+    :param str name: Override the relation :attr:`name`, since it can vary from charm to charm
+    :param list additional_required_keys: Extend the list of :attr:`required_keys`
+    """
+    name = 'db'
+    interface = 'mysql'
+    required_keys = ['host', 'user', 'password', 'database']
+
+
+class HttpRelation(RelationContext):
+    """
+    Relation context for the `http` interface.
+
+    :param str name: Override the relation :attr:`name`, since it can vary from charm to charm
+    :param list additional_required_keys: Extend the list of :attr:`required_keys`
+    """
+    name = 'website'
+    interface = 'http'
+    required_keys = ['host', 'port']
+
+    def provide_data(self):
+        return {
+            'host': hookenv.unit_get('private-address'),
+            'port': 80,
+        }
+
+
+class RequiredConfig(dict):
+    """
+    Data context that loads config options with one or more mandatory options.
+
+    Once the required options have been changed from their default values, all
+    config options will be available, namespaced under `config` to prevent
+    potential naming conflicts (for example, between a config option and a
+    relation property).
+
+    :param list *args: List of options that must be changed from their default values.
+    """
+
+    def __init__(self, *args):
+        self.required_options = args
+        self['config'] = hookenv.config()
+        with open(os.path.join(hookenv.charm_dir(), 'config.yaml')) as fp:
+            self.config = yaml.load(fp).get('options', {})
+
+    def __bool__(self):
+        for option in self.required_options:
+            if option not in self['config']:
+                return False
+            current_value = self['config'][option]
+            default_value = self.config[option].get('default')
+            if current_value == default_value:
+                return False
+            if current_value in (None, '') and default_value in (None, ''):
+                return False
+        return True
+
+    def __nonzero__(self):
+        return self.__bool__()
+
+
+class StoredContext(dict):
+    """
+    A data context that always returns the data that it was first created with.
+
+    This is useful to do a one-time generation of things like passwords, that
+    will thereafter use the same value that was originally generated, instead
+    of generating a new value each time it is run.
+    """
+    def __init__(self, file_name, config_data):
+        """
+        If the file exists, populate `self` with the data from the file.
+        Otherwise, populate with the given data and persist it to the file.
+        """
+        if os.path.exists(file_name):
+            self.update(self.read_context(file_name))
+        else:
+            self.store_context(file_name, config_data)
+            self.update(config_data)
+
+    def store_context(self, file_name, config_data):
+        if not os.path.isabs(file_name):
+            file_name = os.path.join(hookenv.charm_dir(), file_name)
+        with open(file_name, 'w') as file_stream:
+            os.fchmod(file_stream.fileno(), 0600)
+            yaml.dump(config_data, file_stream)
+
+    def read_context(self, file_name):
+        if not os.path.isabs(file_name):
+            file_name = os.path.join(hookenv.charm_dir(), file_name)
+        with open(file_name, 'r') as file_stream:
+            data = yaml.load(file_stream)
+            if not data:
+                raise OSError("%s is empty" % file_name)
+            return data
+
+
+class TemplateCallback(ManagerCallback):
+    """
+    Callback class that will render a Jinja2 template, for use as a ready action.
+
+    :param str source: The template source file, relative to `$CHARM_DIR/templates`
+    :param str target: The target to write the rendered template to
+    :param str owner: The owner of the rendered file
+    :param str group: The group of the rendered file
+    :param int perms: The permissions of the rendered file
+    """
+    def __init__(self, source, target, owner='root', group='root', perms=0444):
+        self.source = source
+        self.target = target
+        self.owner = owner
+        self.group = group
+        self.perms = perms
+
+    def __call__(self, manager, service_name, event_name):
+        service = manager.get_service(service_name)
+        context = {}
+        for ctx in service.get('required_data', []):
+            context.update(ctx)
+        templating.render(self.source, self.target, context,
+                          self.owner, self.group, self.perms)
+
+
+# Convenience aliases for templates
+render_template = template = TemplateCallback
 
=== added file 'hooks/charmhelpers/core/templating.py'
--- hooks/charmhelpers/core/templating.py	1970-01-01 00:00:00 +0000
+++ hooks/charmhelpers/core/templating.py	2014-09-26 07:21:45 +0000
@@ -0,0 +1,51 @@
+import os
+
+from charmhelpers.core import host
+from charmhelpers.core import hookenv
+
+
+def render(source, target, context, owner='root', group='root', perms=0444, templates_dir=None):
+    """
+    Render a template.
+
+    The `source` path, if not absolute, is relative to the `templates_dir`.
+
+    The `target` path should be absolute.
+
+    The context should be a dict containing the values to be replaced in the
+    template.
+
+    The `owner`, `group`, and `perms` options will be passed to `write_file`.
+
+    If omitted, `templates_dir` defaults to the `templates` folder in the charm.
+
+    Note: Using this requires python-jinja2; if it is not installed, calling
+    this will attempt to use charmhelpers.fetch.apt_install to install it.
+    """
+    try:
+        from jinja2 import FileSystemLoader, Environment, exceptions
+    except ImportError:
+        try:
+            from charmhelpers.fetch import apt_install
+        except ImportError:
+            hookenv.log('Could not import jinja2, and could not import '
+                        'charmhelpers.fetch to install it',
+                        level=hookenv.ERROR)
+            raise
+        apt_install('python-jinja2', fatal=True)
+        from jinja2 import FileSystemLoader, Environment, exceptions
+
+    if templates_dir is None:
+        templates_dir = os.path.join(hookenv.charm_dir(), 'templates')
+    loader = Environment(loader=FileSystemLoader(templates_dir))
+    try:
+        source = source
+        template = loader.get_template(source)
+    except exceptions.TemplateNotFound as e:
+        hookenv.log('Could not load template %s from %s.' %
+                    (source, templates_dir),
+                    level=hookenv.ERROR)
+        raise e
+    content = template.render(context)
+    host.mkdir(os.path.dirname(target))
+    host.write_file(target, content, owner, group, perms)
 
=== modified file 'hooks/charmhelpers/fetch/__init__.py'
--- hooks/charmhelpers/fetch/__init__.py	2014-05-08 10:22:43 +0000
+++ hooks/charmhelpers/fetch/__init__.py	2014-09-26 07:21:45 +0000
@@ -1,4 +1,6 @@
 import importlib
+from tempfile import NamedTemporaryFile
+import time
 from yaml import safe_load
 from charmhelpers.core.host import (
     lsb_release
@@ -12,9 +14,9 @@
     config,
     log,
 )
-import apt_pkg
 import os
 
+
 CLOUD_ARCHIVE = """# Ubuntu Cloud Archive
 deb http://ubuntu-cloud.archive.canonical.com/ubuntu {} main
 """
@@ -54,13 +56,68 @@
     'icehouse/proposed': 'precise-proposed/icehouse',
     'precise-icehouse/proposed': 'precise-proposed/icehouse',
     'precise-proposed/icehouse': 'precise-proposed/icehouse',
+    # Juno
+    'juno': 'trusty-updates/juno',
+    'trusty-juno': 'trusty-updates/juno',
+    'trusty-juno/updates': 'trusty-updates/juno',
+    'trusty-updates/juno': 'trusty-updates/juno',
+    'juno/proposed': 'trusty-proposed/juno',
+    'juno/proposed': 'trusty-proposed/juno',
+    'trusty-juno/proposed': 'trusty-proposed/juno',
+    'trusty-proposed/juno': 'trusty-proposed/juno',
 }
 
+# The order of this list is very important. Handlers should be listed in from
+# least- to most-specific URL matching.
+FETCH_HANDLERS = (
+    'charmhelpers.fetch.archiveurl.ArchiveUrlFetchHandler',
+    'charmhelpers.fetch.bzrurl.BzrUrlFetchHandler',
+)
+
+APT_NO_LOCK = 100  # The return code for "couldn't acquire lock" in APT.
+APT_NO_LOCK_RETRY_DELAY = 10  # Wait 10 seconds between apt lock checks.
+APT_NO_LOCK_RETRY_COUNT = 30  # Retry to acquire the lock X times.
+
+
+class SourceConfigError(Exception):
+    pass
+
+
+class UnhandledSource(Exception):
+    pass
+
+
+class AptLockError(Exception):
+    pass
+
+
+class BaseFetchHandler(object):
+
+    """Base class for FetchHandler implementations in fetch plugins"""
+
+    def can_handle(self, source):
+        """Returns True if the source can be handled. Otherwise returns
+        a string explaining why it cannot"""
+        return "Wrong source type"
+
+    def install(self, source):
+        """Try to download and unpack the source. Return the path to the
+        unpacked files or raise UnhandledSource."""
+        raise UnhandledSource("Wrong source type {}".format(source))
+
+    def parse_url(self, url):
+        return urlparse(url)
+
+    def base_url(self, url):
+        """Return url without querystring or fragment"""
+        parts = list(self.parse_url(url))
+        parts[4:] = ['' for i in parts[4:]]
+        return urlunparse(parts)
+
 
 def filter_installed_packages(packages):
     """Returns a list of packages that require installation"""
-    apt_pkg.init()
-    cache = apt_pkg.Cache()
+    cache = apt_cache()
     _pkgs = []
     for package in packages:
         try:
@@ -73,6 +130,16 @@
     return _pkgs
 
 
+def apt_cache(in_memory=True):
+    """Build and return an apt cache"""
+    import apt_pkg
+    apt_pkg.init()
+    if in_memory:
+        apt_pkg.config.set("Dir::Cache::pkgcache", "")
+        apt_pkg.config.set("Dir::Cache::srcpkgcache", "")
+    return apt_pkg.Cache()
+
+
 def apt_install(packages, options=None, fatal=False):
     """Install one or more packages"""
     if options is None:
@@ -87,14 +154,7 @@
         cmd.extend(packages)
     log("Installing {} with options: {}".format(packages,
                                                 options))
-    env = os.environ.copy()
-    if 'DEBIAN_FRONTEND' not in env:
-        env['DEBIAN_FRONTEND'] = 'noninteractive'
-
-    if fatal:
-        subprocess.check_call(cmd, env=env)
-    else:
-        subprocess.call(cmd, env=env)
+    _run_apt_command(cmd, fatal)
 
 
 def apt_upgrade(options=None, fatal=False, dist=False):
@@ -109,24 +169,13 @@
     else:
         cmd.append('upgrade')
     log("Upgrading with options: {}".format(options))
-
-    env = os.environ.copy()
-    if 'DEBIAN_FRONTEND' not in env:
-        env['DEBIAN_FRONTEND'] = 'noninteractive'
-
-    if fatal:
-        subprocess.check_call(cmd, env=env)
-    else:
-        subprocess.call(cmd, env=env)
+    _run_apt_command(cmd, fatal)
 
 
 def apt_update(fatal=False):
     """Update local apt cache"""
     cmd = ['apt-get', 'update']
-    if fatal:
-        subprocess.check_call(cmd)
-    else:
-        subprocess.call(cmd)
+    _run_apt_command(cmd, fatal)
 
 
 def apt_purge(packages, fatal=False):
@@ -137,10 +186,7 @@
     else:
         cmd.extend(packages)
     log("Purging {}".format(packages))
-    if fatal:
-        subprocess.check_call(cmd)
-    else:
-        subprocess.call(cmd)
+    _run_apt_command(cmd, fatal)
 
 
 def apt_hold(packages, fatal=False):
@@ -151,6 +197,7 @@
     else:
         cmd.extend(packages)
     log("Holding {}".format(packages))
+
     if fatal:
         subprocess.check_call(cmd)
     else:
@@ -158,6 +205,28 @@
 
 
 def add_source(source, key=None):
+    """Add a package source to this system.
+
+    @param source: a URL or sources.list entry, as supported by
+    add-apt-repository(1). Examples::
+
+        ppa:charmers/example
+        deb https://stub:[e-mail]/ubuntu trusty main
+
+    In addition:
+        'proposed:' may be used to enable the standard 'proposed'
+        pocket for the release.
+        'cloud:' may be used to activate official cloud archive pockets,
+        such as 'cloud:icehouse'
+
+    @param key: A key to be added to the system's APT keyring and used
+    to verify the signatures on packages. Ideally, this should be an
+    ASCII format GPG public key including the block headers. A GPG key
+    id may also be used, but be aware that only insecure protocols are
+    available to retrieve the actual public key from a public keyserver
+    placing your Juju environment at risk. ppa and cloud archive keys
+    are securely added automtically, so sould not be provided.
+    """
     if source is None:
         log('Source is not present. Skipping')
         return
@@ -182,76 +251,96 @@
         release = lsb_release()['DISTRIB_CODENAME']
         with open('/etc/apt/sources.list.d/proposed.list', 'w') as apt:
             apt.write(PROPOSED_POCKET.format(release))
+    else:
+        raise SourceConfigError("Unknown source: {!r}".format(source))
+
     if key:
-        subprocess.check_call(['apt-key', 'adv', '--keyserver',
-                               'hkp://keyserver.ubuntu.com:80', '--recv',
-                               key])
-
-
-class SourceConfigError(Exception):
-    pass
+        if '-----BEGIN PGP PUBLIC KEY BLOCK-----' in key:
+            with NamedTemporaryFile() as key_file:
+                key_file.write(key)
+                key_file.flush()
+                key_file.seek(0)
+                subprocess.check_call(['apt-key', 'add', '-'], stdin=key_file)
+        else:
+            # Note that hkp: is in no way a secure protocol. Using a
+            # GPG key id is pointless from a security POV unless you
+            # absolutely trust your network and DNS.
+            subprocess.check_call(['apt-key', 'adv', '--keyserver',
+                                   'hkp://keyserver.ubuntu.com:80', '--recv',
+                                   key])
 
 
 def configure_sources(update=False,
                       sources_var='install_sources',
                       keys_var='install_keys'):
     """
-    Configure multiple sources from charm configuration
+    Configure multiple sources from charm configuration.
+
+    The lists are encoded as yaml fragments in the configuration.
+    The frament needs to be included as a string. Sources and their
+    corresponding keys are of the types supported by add_source().
 
     Example config:
-        install_sources:
+        install_sources: |
           - "ppa:foo"
           - "http://example.com/repo precise main"
-        install_keys:
+        install_keys: |
           - null
           - "a1b2c3d4"
 
     Note that 'null' (a.k.a. None) should not be quoted.
     """
-    sources = safe_load(config(sources_var))
-    keys = config(keys_var)
-    if keys is not None:
-        keys = safe_load(keys)
-    if isinstance(sources, basestring) and (
-            keys is None or isinstance(keys, basestring)):
-        add_source(sources, keys)
+    sources = safe_load((config(sources_var) or '').strip()) or []
+    keys = safe_load((config(keys_var) or '').strip()) or None
+
+    if isinstance(sources, basestring):
+        sources = [sources]
+
+    if keys is None:
+        for source in sources:
+            add_source(source, None)
     else:
-        if not len(sources) == len(keys):
-            msg = 'Install sources and keys lists are different lengths'
-            raise SourceConfigError(msg)
-        for src_num in range(len(sources)):
-            add_source(sources[src_num], keys[src_num])
+        if isinstance(keys, basestring):
+            keys = [keys]
+
+        if len(sources) != len(keys):
+            raise SourceConfigError(
+                'Install sources and keys lists are different lengths')
+        for source, key in zip(sources, keys):
+            add_source(source, key)
     if update:
         apt_update(fatal=True)
 
-# The order of this list is very important. Handlers should be listed in from
-# least- to most-specific URL matching.
-FETCH_HANDLERS = (
-    'charmhelpers.fetch.archiveurl.ArchiveUrlFetchHandler',
-    'charmhelpers.fetch.bzrurl.BzrUrlFetchHandler',
-)
-
-
-class UnhandledSource(Exception):
-    pass
-
-
-def install_remote(source):
+
+def install_remote(source, *args, **kwargs):
     """
     Install a file tree from a remote source
 
     The specified source should be a url of the form:
         scheme://[host]/path[#[option=value][&...]]
 
-    Schemes supported are based on this modules submodules
-    Options supported are submodule-specific"""
+    Schemes supported are based on this modules submodules.
+    Options supported are submodule-specific.
+    Additional arguments are passed through to the submodule.
+
+    For example::
+
+        dest = install_remote('http://example.com/archive.tgz',
+                              checksum='deadbeef',
+                              hash_type='sha1')
+
+    This will download `archive.tgz`, validate it using SHA1 and, if
+    the file is ok, extract it and return the directory in which it
+    was extracted.  If the checksum fails, it will raise
+    :class:`charmhelpers.core.host.ChecksumError`.
+    """
     # We ONLY check for True here because can_handle may return a string
     # explaining why it can't handle a given source.
     handlers = [h for h in plugins() if h.can_handle(source) is True]
     installed_to = None
     for handler in handlers:
         try:
-            installed_to = handler.install(source)
+            installed_to = handler.install(source, *args, **kwargs)
         except UnhandledSource:
             pass
     if not installed_to:
@@ -265,30 +354,6 @@
     return install_remote(source)
 
 
-class BaseFetchHandler(object):
-
-    """Base class for FetchHandler implementations in fetch plugins"""
-
-    def can_handle(self, source):
-        """Returns True if the source can be handled. Otherwise returns
-        a string explaining why it cannot"""
-        return "Wrong source type"
-
-    def install(self, source):
-        """Try to download and unpack the source. Return the path to the
-        unpacked files or raise UnhandledSource."""
-        raise UnhandledSource("Wrong source type {}".format(source))
-
-    def parse_url(self, url):
-        return urlparse(url)
-
-    def base_url(self, url):
-        """Return url without querystring or fragment"""
-        parts = list(self.parse_url(url))
-        parts[4:] = ['' for i in parts[4:]]
-        return urlunparse(parts)
-
-
 def plugins(fetch_handlers=None):
     if not fetch_handlers:
         fetch_handlers = FETCH_HANDLERS
@@ -306,3 +371,40 @@
             log("FetchHandler {} not found, skipping plugin".format(
                 handler_name))
     return plugin_list
+
+
+def _run_apt_command(cmd, fatal=False):
+    """
+    Run an APT command, checking output and retrying if the fatal flag is set
+    to True.
+
+    :param: cmd: str: The apt command to run.
+    :param: fatal: bool: Whether the command's output should be checked and
+        retried.
+    """
+    env = os.environ.copy()
+
+    if 'DEBIAN_FRONTEND' not in env:
+        env['DEBIAN_FRONTEND'] = 'noninteractive'
+
+    if fatal:
+        retry_count = 0
+        result = None
+
+        # If the command is considered "fatal", we need to retry if the apt
+        # lock was not acquired.
+
+        while result is None or result == APT_NO_LOCK:
+            try:
+                result = subprocess.check_call(cmd, env=env)
+            except subprocess.CalledProcessError, e:
+                retry_count = retry_count + 1
+                if retry_count > APT_NO_LOCK_RETRY_COUNT:
+                    raise
+                result = e.returncode
+                log("Couldn't acquire DPKG lock. Will retry in {} seconds."
+                    "".format(APT_NO_LOCK_RETRY_DELAY))
+                time.sleep(APT_NO_LOCK_RETRY_DELAY)
+
+    else:
+        subprocess.call(cmd, env=env)
 
=== modified file 'hooks/charmhelpers/fetch/archiveurl.py'
--- hooks/charmhelpers/fetch/archiveurl.py	2014-04-17 10:53:00 +0000
+++ hooks/charmhelpers/fetch/archiveurl.py	2014-09-26 07:21:45 +0000
@@ -1,6 +1,8 @@
 import os
 import urllib2
+from urllib import urlretrieve
 import urlparse
+import hashlib
 
 from charmhelpers.fetch import (
     BaseFetchHandler,
@@ -10,11 +12,19 @@
     get_archive_handler,
     extract,
 )
-from charmhelpers.core.host import mkdir
+from charmhelpers.core.host import mkdir, check_hash
 
 
 class ArchiveUrlFetchHandler(BaseFetchHandler):
-    """Handler for archives via generic URLs"""
+    """
+    Handler to download archive files from arbitrary URLs.
+
+    Can fetch from http, https, ftp, and file URLs.
+
+    Can install either tarballs (.tar, .tgz, .tbz2, etc) or zip files.
+
+    Installs the contents of the archive in $CHARM_DIR/fetched/.
+    """
     def can_handle(self, source):
         url_parts = self.parse_url(source)
         if url_parts.scheme not in ('http', 'https', 'ftp', 'file'):
@@ -24,6 +34,12 @@
         return False
 
     def download(self, source, dest):
+        """
+        Download an archive file.
+
+        :param str source: URL pointing to an archive file.
+        :param str dest: Local path location to download archive file to.
+        """
         # propogate all exceptions
         # URLError, OSError, etc
         proto, netloc, path, params, query, fragment = urlparse.urlparse(source)
@@ -48,7 +64,30 @@
                 os.unlink(dest)
             raise e
 
-    def install(self, source):
+    # Mandatory file validation via Sha1 or MD5 hashing.
+    def download_and_validate(self, url, hashsum, validate="sha1"):
+        tempfile, headers = urlretrieve(url)
+        check_hash(tempfile, hashsum, validate)
+        return tempfile
+
+    def install(self, source, dest=None, checksum=None, hash_type='sha1'):
+        """
+        Download and install an archive file, with optional checksum validation.
+
+        The checksum can also be given on the `source` URL's fragment.
+        For example::
+
+            handler.install('http://example.com/file.tgz#sha1=deadbeef')
+
+        :param str source: URL pointing to an archive file.
+        :param str dest: Local destination path to install to. If not given,
+            installs to `$CHARM_DIR/archives/archive_file_name`.
+        :param str checksum: If given, validate the archive file after download.
+        :param str hash_type: Algorithm used to generate `checksum`.
+            Can be any hash alrgorithm supported by :mod:`hashlib`,
+            such as md5, sha1, sha256, sha512, etc.
+
+        """
         url_parts = self.parse_url(source)
         dest_dir = os.path.join(os.environ.get('CHARM_DIR'), 'fetched')
         if not os.path.exists(dest_dir):
@@ -60,4 +99,10 @@
             raise UnhandledSource(e.reason)
         except OSError as e:
             raise UnhandledSource(e.strerror)
-        return extract(dld_file)
+        options = urlparse.parse_qs(url_parts.fragment)
+        for key, value in options.items():
+            if key in hashlib.algorithms:
+                check_hash(dld_file, value, key)
+        if checksum:
+            check_hash(dld_file, checksum, hash_type)
+        return extract(dld_file, dest)
 
=== modified file 'hooks/charmhelpers/fetch/bzrurl.py'
--- hooks/charmhelpers/fetch/bzrurl.py	2014-02-19 14:49:31 +0000
+++ hooks/charmhelpers/fetch/bzrurl.py	2014-09-26 07:21:45 +0000
@@ -39,7 +39,8 @@
     def install(self, source):
         url_parts = self.parse_url(source)
         branch_name = url_parts.path.strip("/").split("/")[-1]
-        dest_dir = os.path.join(os.environ.get('CHARM_DIR'), "fetched", branch_name)
+        dest_dir = os.path.join(os.environ.get('CHARM_DIR'), "fetched",
+                                branch_name)
         if not os.path.exists(dest_dir):
             mkdir(dest_dir, perms=0755)
         try: